/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.sanselan.common.byteSources;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;

public class ByteSourceInputStream extends ByteSource
{
	private final InputStream is;
	private CacheBlock cacheHead = null;
	private static final int BLOCK_SIZE = 1024;

	public ByteSourceInputStream(InputStream is, String filename)
	{
		super(filename);
		this.is = new BufferedInputStream(is);
	}

	private class CacheBlock
	{
		public final byte bytes[];
		private CacheBlock next = null;
		private boolean triedNext = false;

		public CacheBlock(final byte[] bytes)
		{
			this.bytes = bytes;
		}

		public CacheBlock getNext() throws IOException
		{
			if (null != next)
				return next;
			if (triedNext)
				return null;
			triedNext = true;
			next = readBlock();
			return next;
		}

	}

	private byte readBuffer[] = null;

	private CacheBlock readBlock() throws IOException
	{
		if (null == readBuffer)
			readBuffer = new byte[BLOCK_SIZE];

		int read = is.read(readBuffer);
		if (read < 1)
			return null;
		else if (read < BLOCK_SIZE)
		{
			// return a copy.
			byte result[] = new byte[read];
			System.arraycopy(readBuffer, 0, result, 0, read);
			return new CacheBlock(result);
		}
		else
		{
			// return current buffer.
			byte result[] = readBuffer;
			readBuffer = null;
			return new CacheBlock(result);
		}
	}

	private CacheBlock getFirstBlock() throws IOException
	{
		if (null == cacheHead)
			cacheHead = readBlock();
		return cacheHead;
	}

	private class CacheReadingInputStream extends InputStream
	{
		private CacheBlock block = null;
		private boolean readFirst = false;
		private int blockIndex = 0;

		public int read() throws IOException
		{
			if (null == block)
			{
				if (readFirst)
					return -1;
				block = getFirstBlock();
				readFirst = true;
			}

			if (block != null && blockIndex >= block.bytes.length)
			{
				block = block.getNext();
				blockIndex = 0;
			}

			if (null == block)
				return -1;

			if (blockIndex >= block.bytes.length)
				return -1;

			return 0xff & block.bytes[blockIndex++];
		}

		public int read(byte b[], int off, int len) throws IOException
		{
			// first section copied verbatim from InputStream
			if (b == null)
				throw new NullPointerException();
			else if ((off < 0) || (off > b.length) || (len < 0)
					|| ((off + len) > b.length) || ((off + len) < 0))
				throw new IndexOutOfBoundsException();
			else if (len == 0)
				return 0;

			// optimized block read

			if (null == block)
			{
				if (readFirst)
					return -1;
				block = getFirstBlock();
				readFirst = true;
			}

			if (block != null && blockIndex >= block.bytes.length)
			{
				block = block.getNext();
				blockIndex = 0;
			}

			if (null == block)
				return -1;

			if (blockIndex >= block.bytes.length)
				return -1;

			int readSize = Math.min(len, block.bytes.length - blockIndex);
			System.arraycopy(block.bytes, blockIndex, b, off, readSize);
			blockIndex += readSize;
			return readSize;
		}

	}

	public InputStream getInputStream() throws IOException
	{
		return new CacheReadingInputStream();
	}

	public byte[] getBlock(int start, int length) throws IOException
	{
		InputStream is = getInputStream();
		is.skip(start);

		byte bytes[] = new byte[length];
		int total = 0;
		while (true)
		{
			int read = is.read(bytes, total, bytes.length - total);
			if (read < 1)
				throw new IOException("Could not read block.");
			total += read;
			if (total >= length)
				return bytes;
		}
	}

	private Long length = null;

	public long getLength() throws IOException
	{
		if (length != null)
			return length.longValue();

		InputStream is = getInputStream();
		long result = 0;
		long skipped;
		while ((skipped = is.skip(1024)) > 0)
			result += skipped;
		length = new Long(result);
		return result;
	}

	public byte[] getAll() throws IOException
	{
		ByteArrayOutputStream baos = new ByteArrayOutputStream();

		CacheBlock block = getFirstBlock();
		while (block != null)
		{
			baos.write(block.bytes);
			block = block.getNext();
		}
		return baos.toByteArray();
	}

	public String getDescription()
	{
		return "Inputstream: '" + filename + "'";
	}

}